A vertical-cavity surface-emitting laser (VCSEL) is a type of semiconductor laser diode with laser beam emission perpendicular from a top surface. VCSELs differ from other types of edge-emitting semiconductor lasers that emit laser beams from surfaces formed by cleaving an individual chip out of a wafer. The perpendicular emission of the laser from a VCSEL allows a VCSEL to be tested at various stages throughout the fabrication process to check for material quality and processing issues, unlike edge-emitting lasers that cannot be tested until the end of a production process. Thus, if an edge-emitting laser does not work at the end of the fabrication process, the production time and the processing materials have been wasted.